admin: replace time(nullptr) with timesource's SystemTime (#9740)
admin: replace time(nullptr) with timesource's SystemTime (#9740)

Signed-off-by: Derek Argueta <7ca26d8611d7a7954bc67eac5286d36c49081bac@pinterest.com>

envoyproxy/envoy,eklitzke/envoy,lyft/envoy,envoyproxy/envoy,envoyproxy/envoy,lizan/envoy,lyft/envoy,lyft/envoy,envoyproxy/envoy,lizan/envoy,istio/envoy,envoyproxy/envoy,envoyproxy/envoy,lyft/envoy,istio/envoy,envoyproxy/envoy-wasm,lizan/envoy,envoyproxy/envoy-wasm,eklitzke/envoy,envoyproxy/envoy,envoyproxy/envoy-wasm,eklitzke/envoy,istio/envoy,eklitzke/envoy,eklitzke/envoy,istio/envoy,envoyproxy/envoy,envoyproxy/envoy-wasm,lizan/envoy,istio/envoy,lizan/envoy,lyft/envoy,envoyproxy/envoy-wasm,envoyproxy/envoy-wasm,envoyproxy/envoy,eklitzke/envoy,envoyproxy/envoy,envoyproxy/envoy,envoyproxy/envoy,istio/envoy,istio/envoy,lyft/envoy,lizan/envoy,envoyproxy/envoy-wasm